The present invention relates to machines for the production and/or processing of rod-shaped articles which constitute or form part of smokers' products. Such articles include plain or filter tipped cigarettes, cigars, cigarillos and filter elements of unit length or multiple unit length. More particularly, the invention relates to improvements in apparatus for monitoring certain parts or units of such machines for the presence or absence of rod-shaped articles. Still more particularly, the invention relates to apparatus which can be used to determine the continuity or lack of continuity of a file of rod-shaped articles wherein the articles are located one behind the other and move lengthwise. Such files of articles develop in a machine for the making of plain cigarettes, cigars or cigarillos as a result of subdivision of a continuous tobacco-containing rod into discrete rod-shaped articles, as well as in a filter making machine wherein a rod containing acetate fibers or other suitable filter material is subdivided into discrete rod-shaped sections or filter elements of desired length. The invention will be described in connection with the making of plain cigarettes; however, it is to be understood that machines for the production of plain cigarettes constitute but one of several types of machines which can embody or which can be combined with the improved apparatus. The aforementioned machines for the making of filter elements are another typical example of machines wherein the monitoring apparatus of the present invention can be put to use.
A machine for the making of plain cigarettes includes a distributor which forms a continuous tobacco stream, one or more trimming or equalizing devices which convert the stream into a rodlike tobacco filler, means for draping a web of cigarette paper around the filler to form a continuous rod, and a cutoff or analogous means for subdividing the rod into plain cigarettes of desired length. Plain cigarettes which are obtained as a result of severing of the rod form a normally continuous file, and successive cigarettes of such file are caused to advance past a rotary cam which accelerates the cigarettes and causes them to enter successive flutes of a rotary drum-shaped row forming conveyor. The latter converts the file into one or more rows wherein the cigarettes move sideways, and such rows are advanced into a filter cigarette making machine, into a charger or tray, or to the magazine of a packing machine.
If the continuity of the file is interrupted, e.g., as a result of breakage of the rod and/or cigarette paper web, the prime mover of the machine should be arrested with a minimum of delay in order to avoid a pileup of tobacco, cigarette paper and/or cigarettes. To this end, the file of cigarettes is monitored (normally in the region of the cutoff) in order to immediately detect the absence of cigarettes and to produce a signal which is used to arrest the prime mover so that the attendants can eliminate the cause of malfunction and restart the machine as soon as possible.
Presently known monitoring apparatus comprise photoelectric cells which are mounted adjacent to the path of movement of the file of cigarettes downstream of the cutoff. If the interval between the passage of two successive cigarettes between the light source and the photoelectric transducer of the cell is too long, the transducer transmits a signal which is amplified and used to arrest the prime mover of the machine. A drawback of such apparatus is that their operation is unduly affected by solid particles (especially tobacco dust) which are invariably present in the area surrounding the cutoff. Such particles settle on the lens system of the cell and/or light-sensitive surface of the transducer and prevent the cell from producing a signal in response to absence of cigarettes at the monitoring station. The situation is aggravated if the prime mover of the cigarette maker also serves to drive at least one other machine, such as a filter cigarette making machine. This compounds the losses in tobacco and filter material, especially in a modern production line which turns out up to and in excess of 70 smokers' products per second.